I-15 DEMONSTRATES SANDAG’S WISDOM

Adding four new lanes to Interstate 15 has cut the average commute by a whopping 25 percent compared with a decade ago, the San Diego Association of Governments concluded recently.

If this news seems fairly obvious — that expanding roads can fix traffic jams — it flies in the face of four decades of state and federal policymaking, which diverted billions of gasoline tax dollars into rail and bus systems on the theory that building freeways makes traffic worse, because people just drive more.

Such folly originated with the “Law of Peak-Hour Traffic Congestion” proposed in 1962 by public policy analyst Anthony Downs. It was seized upon in the 1970s by environmental activists and sympathetic lawmakers who sparked a historic boom in public transit spending that continues today.

In 2011, a landmark study by economists Gilles Duranton and Matthew A. Turner found evidence to support Downs’ theory — traffic does expand to fill new lanes. Put another way, if you give people more freedom, they will use it.

But the economists also found that massive transit spending has done nothing to cut congestion. Their suggestion: Use “congestion pricing,” which charges tolls that rise as traffic builds.

Despite the objections of activists, this toll-lane concept is precisely what SANDAG built on I-15 — and what it proposes for Interstate 5 and state Route 78.